Investment Calculator
Free investment calculator.
Project what an investment could grow to over time. Enter a starting amount, a regular monthly contribution, an expected annual return, and how many years you'll invest — the calculator combines lump-sum growth with your ongoing contributions and shows the projected balance, how much you contributed, and how much came from growth.
Seeing the split between what you put in and what compounding added is the clearest way to understand why long horizons matter so much.
How contributions and compounding combine
This projection has two engines. Your starting amount grows on its own, compounding month after month. Your monthly contributions form a second stream, where each deposit begins compounding from the moment it's added — so early contributions do far more work than later ones. Add the two together and you get the future balance. The breakdown separates the total you actually contributed from the growth on top, which is usually the more motivating number: over a long horizon, growth often dwarfs contributions.
Choosing a realistic return
The return you assume drives everything, so choose it thoughtfully. Broad stock-market averages have historically landed near 7% a year after inflation over long periods, but real returns are volatile — some years are strongly positive, others negative — and past performance never guarantees the future. A more conservative figure gives a safer plan; an optimistic one flatters the result. Because the calculator assumes a smooth, constant rate, treat its output as a planning estimate rather than a promise, and remember it isn't financial advice. Running the numbers with a couple of different return assumptions is the honest way to see a realistic range.
Dollar-cost averaging and staying invested
The monthly-contribution model here mirrors how most people actually invest: steadily, a bit each month, rather than in one lump sum. Contributing on a fixed schedule regardless of price is known as dollar-cost averaging, and its appeal is behavioural as much as mathematical — it removes the temptation to time the market and keeps you investing through downturns, which is exactly when future returns are being seeded. The projection assumes you leave the money invested and let it compound. Withdrawing early, or stopping contributions, changes the outcome dramatically, which you can see by shortening the years or lowering the monthly amount.
Frequently asked questions
How is this different from the compound interest calculator?
The maths is related, but this tool is framed around investing with regular contributions and an expected market return, and it highlights the contributed-versus-growth split. The compound interest tool focuses on a set interest rate and compounding frequency.
Does it account for inflation or taxes?
No. The projection is in nominal terms before tax. For a real (inflation-adjusted) view, enter a return net of expected inflation.
What return should I use?
That's your judgement call. Many long-term planners use a conservative single-digit percentage; test a few values to see a range rather than a single point.
Should I invest a lump sum or spread it out?
Both are valid strategies with different trade-offs, and the best choice depends on your circumstances and risk tolerance. This tool models regular contributions; it isn't financial advice.
Last updated: 2026-01-20